These images of an asteroid that is at least 3,600 feet (1,100 meters) long were taken on Dec. 17, 2015, (left) and Dec. 22 (right) by scientists using NASA's 230-foot (70-meter) Deep Space Network antenna at Goldstone, California. This asteroid, named 2003 SD2020, will safely fly past Earth on Thursday, Dec. 24, at a distance of 6.8 million miles (11 million kilometers). On Dec. 17, it was about 7.3 million miles (12 million kilometers) from Earth. By Dec. 22, it was closing in on its Christmas Eve flyby distance. – Image Credits: NASA/JPL-Caltech/GSSR

Asteroid 2003 SD220 will safely fly past Earth on Dec. 24 at a distance of 6.8 million miles (11 million kilometers). Scientists at NASA's Jet Propulsion Laboratory in Pasadena, California, have generated the highest-resolution images to date of this asteroid using the Deep Space Network's 230-foot (70-meter) antenna at Goldstone, California. The radar images were acquired between Dec. 17 and Dec. 22, when the distance to this near-Earth object (NEO) was narrowing from 7.3 million miles (12 million kilometers) to almost the flyby distance.

"The radar images data suggest that asteroid 2003 SD220 is highly elongated and at least 3,600 feet [1,100 meters] in length," said Lance Benner of JPL, who leads NASA's asteroid radar research program. "The data acquired during this pass of the asteroid will help us plan for radar imaging during its upcoming closer approach in 2018."

Three years from now, the asteroid will safely fly past Earth again, but even closer, at a distance of 1.8 million miles (2.8 million kilometers). The 2018 flyby will be the closest the asteroid will get to Earth until 2070, when it is expected to safely fly past our planet at a distance of about 1.7 million miles (2.7 million kilometers).

"There is no cause for concern over the upcoming flyby of asteroid 2003 SD220 this Christmas Eve," said Paul Chodas, manager of NASA's Center for NEO Studies at JPL. "The closest this object will come to Santa and his eight tiny reindeer is about 28 times the distance between Earth and the moon."

Radar has been used to observe hundreds of asteroids. When these primitive denizens of the solar system pass relatively close to Earth, radar is a powerful technique for studying their sizes, shapes, rotation, surface features and roughness, and for improving the calculation of their orbits.

JPL hosts the Center for Near-Earth Object Studies for NASA's Near-Earth Object Observations Program within the agency's Science Mission Directorate.

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Mathematical physicist and cosmologist Stephen Hawking was best known for his work exploring the relationship between black holes and quantum physics. A black hole is the remnant of a dying supermassive star that’s fallen into itself; these remnants contract to such a small size that gravity is so strong even light cannot escape from them. Black holes loom large in the popular imagination – schoolchildren ponder why the whole universe doesn’t collapse into one. But Hawking’s careful theoretical work filled in some of the holes in physicists’ knowledge about black holes.

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For decades, ever since the Pioneer and Voyager missions passed through the outer Solar System, scientists have speculated that life might exist within icy bodies like Jupiter’s moon Europa. However, thanks the Cassini mission, scientists now believe that other moons in the outer Solar System – such as Saturn’s moon Enceladus – could possibly harbor life as well.

Enceladus, one of Saturn's moons, is currently a leading candidate for scientists searching for the ingredients for extraterrestrial life. One new study shows how microorganisms could survive there, living off of methane.

When we finally find life somewhere out there beyond Earth, it’ll be at the end of a long search. Life probably won’t announce its presence to us, we’ll have to follow a long chain of clues to find it. Like scientists keep telling us, at the start of that chain of clues is water.

Finding past or present microbial life on Mars would without doubt be one of the greatest scientific discoveries of all time. And in just two years’ time, there’s a big opportunity to do so, with two rovers launching there to look for signs of life – Mars2020 by NASA and ExoMars by the European Space Agency and Roscosmos.

It has been theorized that a world could be habitable even if doesn't orbit a star. After the expulsion of moons from solar systems, moons and planets could be close enough to create tidal heating, potentially making a rogue moon habitable.